Production of fluoroelastomers by emulsion and solution polymerization methods is well known in the art; see for example U.S. Pat. Nos. 4,214,060; 4,281,092; 6,512,063 and 6,774,164 B2. Generally, fluoroelastomers are produced in an emulsion polymerization process wherein a water-soluble polymerization initiator and a relatively large amount of dispersing agent (i.e. surfactant) are employed.
Benning (U.S. Pat. Nos. 2,559,749 and 2,597,702) discloses fluorinated aliphatic phosphates that may be employed as emulsifying agents in the aqueous polymerization of unsaturated organic compounds. These phosphate esters are said to be particularly useful in the polymerization of tetrafluoroethylene (TFE) and chlorotrifluoroethylene (CTFE) homopolymers.
Urban (U.S. Patent Application Publication 2006/0229398 A1) discloses the polymerization of fluoromonomers with (meth)acrylates in an aqueous system that employs both 1) a fluoroalkylphosphoric acid ester salt such as phosphoric acid bis(tridecafluorooctyl)ester ammonium salt, and 2) an anionic alkyl sulfonate surfactant such as sodium dodecyl sulfate.
Morgan et al. (U.S. Pat. No. 6,395,848 B1) disclose an aqueous dispersion process utilizing a combination of at least two fluorosurfactants. At least one surfactant is a perfluoropolyether (PFPE) carboxylic acid, sulfonic acid or the salt thereof and at least one surfactant is a fluoroalkyl carboxylic acid, sulfonic acid or the salt thereof, or a fluoroalkoxy aryl sulfonic acid or salt thereof.